title: Inhibition of Ca2+ of carbamoylphosphate synthetase (ammonia).
abstract: The effect of Ca2+ ions on carbamoylphosphate synthetase (ammonia) (EC 6.3.4.16) of rat liver mitochondria was studied. In lysed mitochondria, carbamoylphosphate synthetase (ammonia) was inhibited by Ca2+ ions. In intact rat liver mitochondria, the rate of citrulline production from added ammonia, ornithine, and bicarbonate was inversely correlated with the magnitude of the intramitochondrial concentration of Ca2+. This effect was found at concentrations of Ca2+ which are within the physiological range. The inhibition was reversed by added Mg2+ and was not due to effects of Ca2+ on mitochondrial energy production. It is proposed that the activity of carbamoylphosphate synthetase (ammonia) may be modulated in vivo by changes in the concentration of Ca2+ ions in the mitochondrial matrix.
mesh_terms: D000818:Animals; D002118:Calcium / Q000494:pharmacology*; D002222:Carbamoyl-Phosphate Synthase (Ammonia) / Q000037:antagonists & inhibitors*; D002956:Citrulline / Q000096:biosynthesis; D004533:Egtazic Acid / Q000494:pharmacology; D007700:Kinetics; D008025:Ligases / Q000037:antagonists & inhibitors*; D008274:Magnesium / Q000494:pharmacology; D008297:Male; D008930:Mitochondria, Liver / Q000201:enzymology*; D051381:Rats
chemical_list: D002956:Citrulline; D004533:Egtazic Acid; D008025:Ligases; D002222:Carbamoyl-Phosphate Synthase (Ammonia); D008274:Magnesium; D002118:Calcium